Probe apparatus for correcting the probe card posture before testing

ABSTRACT

A probe apparatus including a table on which a semiconductor wafer is mounted, for a wafer having a circuit connected to a plurality of pads. A probe card assembly is positioned relative to a reference plane, and has a card body and groups of probes held by a card holder. A drive system moves the table up and down to cause the pads to contact probe tips, and a test head sends test signals to the circuit through the probes and pads, which contact one another, to test the electric property of the circuit. In addition, a sensor detects the probe tip profile or levels at plural points of the probe card assembly, and a controller calculates the tilting degree and direction of probe tip profile of probe groups on the basis of the results thus detected to thereby send correction commands. A tilt correction unit supports the card holder and adjusts a level of the card holder at the plural points, in response to the command applied from the controller, to thereby make the probe tip profile or each probe group parallel to the reference plane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a probe apparatus for checking theelectric property of an object such as a semiconductor wafer chip.

2. Description of the Related Art

In the conventional probe apparatus disclosed in Jpn. Pat. Appln. KOKAIPublication No. Sho 64-73632, a probe card is positioned in an apparatusbody through a card holder and a test head is arranged above it.

The probe card mainly used is of the probe-tilted type in which eachprobe as tilted relative to a printed plate. The other probe carddifferent from the probe-tilted one as of the vertical probe type inwhich a plurality of probes extend vertical from the probe card at highdensity. This vertical type probe card (VTPC) has been made to meet thenumber of electrode pads increased and their pitch made finer assemiconductor chips are more and more integrated.

In the conventional probe apparatus, the wafer-mounted table (or waferstage), a head plate and an insert ring are arranged parallel to oneanother. However, the tip level of probes becomes uneven because ofattaching errors of the head plate, the insert ring and a card holder orbecause of making errors and deformation of the probe card itself. Asthe result, level of probe tip portions are differ, and the probe tipprofile is tilted or shifted from its predetermined position relative toa horizontal plane.

"The probe tip profile" corresponds to a plane or a curved surfaceformed by an envelope extending along tips of probes.

In the case of a probe card on which the probe tip profile of each probegroup is tilted or shifted. One tips of probe line or group are put in ahigh level position while the other tips of probe line or group are in alow position. When this tilting of probe tips of one group from those ofthe other group exceeds an allowable value (smaller than 20-30 μm), someof the probes do not contact or incompletely contact with the pads tothereby cause full electric continuity not to be attained even if thewafer on the wafer-mounted table is over-driven or lifted over theircontact point.

In recent years, the number of probes is increased in the probeapparatus now used. It is therefore quite important that the accuracy ofprobe tips of the probe card is high. The tilting or shifting of theprobe tip profile becomes more and more of a serious problemaccordingly. In the conventional probe apparatus, a microscope is set tothe apparatus body, the wafer-mounted table (or wafer chuck) is lifteduntil the wafer is contacted with contact pins, and probe tips of eachprobe group contact with the wafer or their tracks on the wafer arechecked through the microscope. When the probe tip profile of each probegroup is tilted or shifted from their predetermined position, the probecard is re-set in the apparatus body or fasteners for the head plate areunfastened and a spacer is inserted between the head plate and itsreference plane.

However, it is quite difficult to check the tilting of the probe tiplevel through the microscope. In addition, it is also quite difficult tofind the location to insert the spacer under the head plate. Further,the probe card is not manufactured to meet the condition under which itencounters in the probe apparatus. Every probe card, therefore, canbecome deformed. When a heavy test head is arranged above the probe cardpractically set, another tilting of the probe tip profile is caused andit is quite troublesome to correct it.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide a probeapparatus capable of more easily detecting the tilting of the probe tipprofile of each probe group, which is caused by making and attachingerrors and deformation of the probe card, under such a condition thatthe probe card is practically set in the apparatus, and also capable ofby far more easily and reliably correcting this tilting of the probe tipprofile.

According to the present invention, there can be provided a probeapparatus comprising a table on which an object to be tested is mounted,the object having a circuit connected to a plurality of pads; a probecard assembly positioned relative to a reference plane, and having acard body and groups of probes held on a card holder; lifter means formoving the object-mounted table up and down to cause the pads of theobject to be contacted with probe tips of probe groups; a test head forapplying test signal to the circuit of the object through the probes andpads, which are contacted with one another, to test the electricproperty of the circuit; detector means for detecting probe tip profilesor levels at plural points of the probe card assembly; correctioncommand means for calculating a tilting degree and direction of eachprobe group from results thus detected to send correction commands; andtilt correction means for supporting the card holder and adjusting eachof levels of the card holder at the plural points, responsive tocommands applied from the correction command means, to make the probetip profiles of each probe group parallel to the reference plane.

The probe tip profile detector means includes a displacement sensor ofthe contact type set on the table on which the object to be tested isalso mounted and has plural individual detection areas which arecontacted with probes of the probe card when the table is lifted, and adetector circuit for detecting changes in voltage caused when eachdetection area of the contact type displacement sensor is contacted withprobes. It is therefore desirable that the probe tip profile of eachprobe group is detected responsive to signal applied from the detectorcircuit and on the basis of a distance over which the table is lifted.

It as preferable that the probe tip profile detector means includes acamera through which the image of probe tip profile of probes is takenat plural sections, and a detector circuit for detecting the probe tipprofile of probes at plural sections from focus depths of the camera.

The probe tip profile detector means may include a conductive dummyplate mounted on the table, and a contact-check-programmed tester forchecking whether or not probes are contacted with the dummy plate. Whenarranged as described above, the probe tip level of probes can bedetected at plural sections, responsive to signals applied from thetester and on the basis of a distance over which the table is lifted.

It is desirable that the card holder, insert ring or head plate issupported at least at three points thereof by the tilt correction unit.It is also desirable that the tilt correction unit has a ball hingemechanism arranged at least one of the three points to support the cardholder and others, and level adjustment screw mechanisms arranged atleast at the other two points to adjust levels of the card holder andothers.

Each level adjustment screw mechanism may include a manual adjustmentscrew having a graduated dial or a ball screw provided with an autodrivemotor.

In order to carry out the probe test with a higher accuracy, it isneeded that the test head and the object to be tested are kept parallelto each other. There may be provided test head adjustment mechanisms forsupporting the test head from the apparatus body to adjust the tiltingof it, probe tip measuring means for measuring the parallel of probesrelative to the horizontal reference plane of the object-mounted table,and control means for controlling the test head adjustment mechanismsresponsive to detection signals applied from the probe tip measuringmeans to adjust the tilting of the test head and keep probe tipsparallel to the reference plane.

It is desirable that each test head adjustment mechanism includes amotor arranged in the apparatus body, a crew rod rotated by the motor,and a slider member screwed onto the screw rod and moved up and down, asthe screw rod is rotated, while supporting the test head.

Further, test head adjustment mechanisms capable of supporting the testhead from the apparatus body and adjusting the tilting of the test headmay be provided as means for keeping the test head and the objectparallel to each other. It is desirable in this case to provide probetip measuring means for measuring the parallel (or tilt) of probesrelative to the reference plane, object measuring means for measuringthe parallel of the object mounted on the object-mounted table, andcontrol means for controlling the test head adjustment mechanismsresponsive to detection signals applied from the probe tip and objectmeasuring means to adjust the tilt of the test head and keep probesparallel to the abject to be tested.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 shows the probe apparatus according to a first embodiment of thepresent invention, a part of which is cut away to show its insidearrangement;

FIG. 2 is a perspective view showing a main stage provided with awafer-mounted table, which is used in the probe apparatus;

FIG. 3 is a vertically-sectioned view showing a main portion of thefirst probe apparatus;

FIG. 4 is a plan view showing the main portion of the first probeapparatus;

FIG. 5 is a circuit diagram showing probe tip level detector means ofthe first probe apparatus;

FIG. 6 is a side view showing a wafer-mounted table enlarged, said tablehaving a displacement sensor of the contact type;

FIG. 7 is a block diagram showing a control system in the first probeapparatus;

FIG. 8 is a sectional view showing a probe tip level correction unit;

FIG. 9 is a vertically-sectioned view showing a main portion of theprobe apparatus according to a second embodiment of the presentinvention;

FIG. 10 is a perspective view showing the second probe apparatusdismantled;

FIG. 11 is a perspective view showing a third probe apparatus partly cutaway;

FIG. 12 is a sectional view showing a clamp mechanism of the third probeapparatus enlarged;

FIG. 13 is a schematic illustration showing a probe apparatus accordingto a third embodiment; and

FIG. 14 is a schematic illustration showing a probe apparatus accordingto a fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some probe apparatus according to the present invention used to checksemiconductor chips on a wafer will be described with reference to theaccompanying drawings.

As shown in FIG. 1, reference numeral 11 denotes a probe apparatus bodyshaped like a box and a main stage 13 as arranged on a support 12 in thecenter of the body 11. A table (or wafer chuck) 15 on which asemiconductor wafer 14 is mounted is arranged on the main stage 13. Thewafer-mounted table 15 is mounted on an X-Y-θ table.

A head plate 17 is held horizontal on the top of the apparatus body 11by a rigid support frame 16 which is erected on the support 12. Aninsert ring 18 is positioned in a center opening of the head plate 17and a probe unit 21 is arranged in the insert ring 18. The probe unit 21has a probe card 22 which is held by card holder 25. A plurality ofprobes 23 are attached to the probe card 22, which is previously set ata predetermined position by the holder 25. When the card holder 25 issupported by the insert ring 18, the probe unit 21 is set above and inopposite to the wafer-mounted table 15. A contact ring 26 is arranged onthe probe unit 21 and electrically connected to the probe card 22.

A test head 27 is mounted and supported on the apparatus body 11 inwhich the probe unit 21 has been positioned as described above. It iselectrically contacted with each probe 23 of the probe card 22 and withthe contact ring 25. It is also electrically contacted with an externaltester 28. A microscope or television camera 29 is arranged above it toview the wafer 14 and probe tips contacted with it through a centeropening of the probe card 22. The test head 27 has a weight of about300-400 kg, but the probe card 22 only a weight of about 500-800 g.

An autoloader 31 is arranged on one side of the apparatus body 11. Acassette mount 33 into and out of which a wafer cassette 32 is carried,holding a plurality of wafers 14 therein, is arranged, movable up anddown, in the autoloader 31. A loader stage 34 is arranged adjacent tothe autoloader 31 to pick up wafers 14 one by one out of the wafercassette 32. An auxiliary alignment stage (not shown) is arrangedadjacent to the loader stage 34 to add auxiliary alignment to the wafer14.

A wafer handling arm 35 is arranged between the apparatus body 11 andthe autoloader 31. It serves as a means for mounting the wafer 14, towhich auxiliary alignment has been applied, on the wafer-mounted table(or wafer chuck) 15. This wafer handling arm 35 and the loader stage 34also serve to pick up the wafer 14, which has been tested, from thewafer-mounted table 15 and return it into the wafer cassette 32.

An alignment unit (not shown in FIG. 1) is arranged in the apparatusbody 11 on the center front side thereof. It has an alignment systemprovided with a CCD camera 48 (FIG. 2) or a laser beam (not shown), anda detector circuit 36 provided with an electrostatic capacitance sensor36a. The alignment system is intended to accurately align the wafer 14on the wafer-mounted table 15, using scribe lines and others.

As shown by virtual lines in FIG. 3, the wafer-mounted table 15 can becarried right under the electrostatic capacitance sensor 36a by acarrier system (not shown). The electrostatic capacitance sensor 36aserves to detect the position of the wafer-mounted table 15 in adirection Z and the thickness of the wafer 14 on it.

As shown in FIG. 1, a probe card exchanger 37 is arranged on the leftside of the apparatus body 11. Card holding shelves 38 are provided inthe probe card exchanger 37 and probe cards 22 of various kinds eachhaving the card holder 25 can be stored, freely exchangable, on theshelves 38. If necessary, one of these probe cards 22 are taken out ofthe card holding shelves 38 and set in the insert ring 18 in the centerof the head plate 17. The setting and exchanging operation of the probecard 22 is manually made by the operator or automatically conducted by aunit (not shown) same as the wafer handling arm 16. This automatic probecard exchanger 37 is disclosed in U.S. Pat. No. 4,966,520.

As shown in FIG. 2, the main stage 13 includes a Y table 41 movable ontwo rails 41a extending in a direction Y and an X table 42 movable ontwo rails 42a extending on the Y table 41 in a direction X. Each of themis driven by a drive system (not shown) provided with a pulse motor. Arod 43 between the X table 42 and the wafer-mounted table 15 inconnected to elevation and rotation drive systems (not shown) to drivethe wafer-mounted table 15 in a direction Z and to rotate it (about theaxis Z).

As shown in FIG. 2, an elevation or lifter system 47 is attached to theside of the X table 42 of the main stage 13 and a camera 48 on it ismoved up and down by the lifter system. The moving camera 48 compriseshigh and low magnification units 48a and 48b. On the other hand, a piece49 is fixed to the side of the wafer-mounted table 15, projectinghorizontal from it. Thin conductive film such as ITO (indium tin oxide)is formed on the top of the piece 49 or chrome plating is applied to it,and a target 49a such as a mark or cross is formed in the center of it.

The piece 49 is moved up and down and rotated together with thewafer-mounted table 15 and when it comes on the optical axis of the highmagnification unit 48a of the moving camera 48, the center of its crossmark target 49a serves as a reference point to detect the position ofthe wafer-mounted table 15 in the direction θ (or round the axis Z) bythe moving camera 48. Further, thin conductive film around the target49a on the piece 49 allows the position (or height) of the wafer-mountedtable 15 in the direction Z to be detected by the electrostaticcapacitance sensor 36a. The position control by the alignment unit isdisclosed in Jpn. Pat. Appln. KOKAI Publication No. Sho 64-73632.

A probe card assembly will be described in detail with reference toFIGS. 3 and 4.

A body 24 of the probe card 22 is a printed plate having a centeropening. A plurality of probes 23 are tilted downward from both sides ofthe canter opening of the card body 24. Groups of these probes 23 aresupported by the card body 24 to correspond to those of pads of singleor plural chips. The card body 24 is seated on a step 25a of the cardholder 25 and its outer circumference is positioned and fixed to thecard holder 25 by pins and screws.

The probe card 22 can be detachably set at a position above and inopposite to the wafer-mounted table 15 when the card holder 25 iscontacted with the underside of the insert ring 18 and fastened byfastening means or sandwiched by an automatic setting support ringmovable up and down. The probe card in this case is of the tilted probetype but it may be of the VTPC type.

When the probe card 22 is set to the insert ring 18 in this manner, aplurality of electrodes in the card body (or printed plate) 24 areelectrically connected to the contact ring 26 which is attached to theinsert ring 18. As a result, each probe 23 is electrically connected tothe test head 27 via the contact ring 26 and a pogo pin 26a (FIG. 3).When tips of the probes 23 are contacted with pads on the wafer, testsignal is sent to a circuit and then to an input side of the tester 28.

The elevating (or Z-up) movement of the wafer-mounted table 15 at thetime of probe test will be described.

The wafer-mounted table 15 is lifted from its lowermost referenceposition to a position adjacent to the underside of the probe card 22 athigh speed. It is then lifted at low speed to a height (or contactpoint) where electrode pads on the chip are contacted with the probes23. It is further lifted only by a bit of its stroke at a lower speed toover drive the contact point. It is preferable that the first distancelifted at high speed is set about 20 mm, that the next distance liftedat low speed is about 3-8 mm and that the final distance over-driven isabout 50-100 μm to reliably attain full electric contact between theprobes 23 and the pads.

The head plate 17 is supported horizontal on the support 12, on whichthe wafer-mounted table 15 is also supported, by the rigid support frame16. The insert ring 18 is seated and fitted on a step 17a of the centerhole of the head plate 17. The top of the wafer-mounted table 15, thehead plate 17 and the insert ring 18 are arranged parallel to oneanother.

When the probe card 22 is practically set and positioned in the insertring 18 and the heavy test head 27 is then mounted on them through thecontact ring 26, however, the probe card 22 sometimes causes the levelof probe tips of one probe group to be tilted relative to itself or tothat of probe tips of other probe group. Means for detecting andcorrecting this tilting of the probe tip profile of the probe card 22will be described with reference to FIGS. 3 and 4.

As shown in FIG. 4, a tilt correcting unit 51 serves as means fordetecting and correcting the tilting of the probe tip profile of theprobe card 22. It has a ball hinge mechanism 52 and two adjustment screwmechanisms 53, through which the probe card assembly is supported on thehead plate 17. One adjustment screw mechanism 53 is arranged at afulcrum A while the other at a fulcrum B.

The ball hinge mechanism 52 includes a steel ball 52a and a pair ofstopper screws 52b. The steel ball 52a as arranged between the step 17aof the head plate 17 and a protrusion 18a projected outward from theside of the insert ring 18. It is also positioned in the center betweenthe paired stopper screws 52b.

As shown in FIG. 3, the outer rim portion of the insert ring 18 is puton the step 17a of the head plate 17 and fastened by screws 53b of thetilt correcting unit 51. In short, the tilt correcting unit 51 alsoserves as means for fastening the insert ring 18 to the head plate 17.To add more, the outer diameter of the insert ring 18 is about 2.5-3.5times larger than that of the wafer 14.

Each adjustment screw mechanism 53 has a manual adjustment screw 53a anda stopper screw 53b. The manual adjustment screw 53a has on the headthereof a dial 53d provided with graduations 53c. A protrusion 18bprojected outward from the side of the insert ring 18 can be adjusted toa desired support level while rotating the dial 53d forward or backwardto set one of graduations 53c to a reference arrow. The stroke of eachadjustment screw mechanism 53 is previously determined and the probecard 22 can be adjusted to a level of 1000 μm, maximum, in the directionZ by these adjustment screw mechanisms 53. Although the level of theprobe card 22 is adjusted or changed in this case by manually adjustingthe screws 53a, an automatic adjustment system may be employed using thedistortion of a piezoelement.

A displacement sensor 55 having plural detection areas and a detectioncircuit 60 for detecting voltage changes caused when probes 23 arecontacted with these detection areas of the displacement sensor 55 areprovided as means for detecting the tip level of each probe group of theprobe card 22 practically set. A control system 70 serves as means forconfirming the probe tip profile of each probe group responsive tosignal applied from the detector 60 and also on the basis of thedistance over which the wafer-mounted table 15 is lifted, andarithmetically calculating the tilting degree and direction of the probetip profile of each probe group to thereby provide correction commands.

As shown in FIGS. 5 and 6, the displacement sensor of the contact typeis made flat by a sensor body 56 and a plate 57. The sensor body 56 hasthree layers comprising PVDF (polyvinylidene fluoride) film 56a, 28 μmthick, and electrodes 56b and 56c formed on top and underside of film56a. PVDF is a kind of piezo-plastics.

PVDF film 56a generates voltage between both electrodes 56b and 56c dueto electric polarization phenomenon (or piezoelectric effect) causedwhen mechanical distortion is applied to crystals of film 56a.Electrodes 56b and 56c are conductive foil films each being formed byevaporating aluminium all over the top or underside of film 56a.

Symbols a, b, c and d in FIG. 5 denote detection areas of the body 56 ofthe displacement sensor 55 contacted with probes 23. The displacementsensor 55 is equally divided into four detection areas to allow each ofthem to generate voltage due to piezoelectric effect. More specifically,the electrode 56c on the underside of film 56a is common to all of fourdetection areas and grounded, but PVDF film 56a on the electrode 56c andthe electrode 56b on the top of film 56a are equally divided into fourareas by cross-like grooves to make each area independent of the others.

The plate 57 of the displacement sensor 55 serves to support theresilient sensor body 56 flat and it is silicon wafer or made of glass,epoxy, plastics or others. When it is a conductive plate such as thesilicon wafer, it is supposed to be used as the grounded undersideelectrode 56c for the sensor body 56, but insulation oxide film isapplied to the top of it and the sensor body 56 is then fixed to them byadhesive in this case.

The plate 57 is same in outer diameter and thickness as the wafer 14 andit has an orientation flat. The extremely thin sensor body 56 is onlybonded to it and the displacement sensor 55 of the contact type istherefore substantially same in shape as the wafer 14. This displacementsensor 55 is automatically transferred onto the wafer-mounted table 15,if needed. More specifically, it is housed and stored somewhere in theautoloader 31, carried out by the loader stage 34 and then pre-aligned.After then, it is mounted on the wafer-mounted table 15 by the waferhandling arm 35 and accurately positioned by the alignment unit. Thedetector circuit 60 has four voltmeters 61a, 61b, 61c and 61d on theside of the wafer-mounted table 15 to detect voltage changes caused whendetection areas a, b, c and d of the body 56 of the contact typedisplacement sensor 55 are contacted with probes 23.

The plate 57 of the contact type displacement sensor 55 is provided withcontact terminals 58a, 58b, 58c and 58d, and an earth terminal 58f. Thecontact terminals 58a, 58b, 58c and 58d are connected to lead lines (orprinted wires) extending from the top electrodes 56b of the detectionareas a, b, c and d of the sensor body 56. The earth terminal 58f isconnected to the underside electrode (or common ground) 56c. When thesensor 55 is mounted on the wafer-mounted table 15, electric contact ofdetection areas a, b, c and d with voltmeters 61a-61d can beautomatically attained. To add more, the contact terminals 58a-58d andthe earth terminal 58f are connected to a contact terminal 62 of thedetector circuit 60 which is embedded in the top of the wafer-mountedtable 15.

Referring to FIG. 7, it will be described what relation the controlsystem has to sensors and drive systems.

The control system 70 has a memory-provided CPU 71, to which circuits72, 73 and 74 for controlling movement in the directions, X, Y, Z and θare connected via a system bath. The control circuit 72 is connected tothe X-Y drive system 44, the control circuit 73 to the elevation drivesystem 45 and the control circuit 74 to the rotation drive system 46.

The electrostatic capacitance sensor detecting circuit 36 of thealignment unit is also connected to the CPU 71 via the system bath.Further, the detector circuit 60 of the contact type displacement sensor55 and a circuit 102 for detecting the probe tip level through a CCDcamera are also connected to the CPU 71 through the system bath. Theprobe tip profile of each probe group can be checked on the basis ofdetection signals applied from these detector circuits 36 and 60 and thedistance over which the wafer-mounted table 15 is lifted.

A tilt correction circuit 75 is connected to the CPU 71 through thesystem bath and a display 76 is connected to the tilt correction circuit75. A predetermined soft programming is previously stored in the tiltcorrection circuit 75. The CPU 71 checks the probe tip profile of eachprobe group and arithmetically calculate the tilting degree anddirection of the probe tip profile of the probe group on the basis ofthe result thus obtained to thereby show a command to correct thetilting of the probe tip profile on the display 76.

The command to correct the tilting of the probe tip profile is seen inthe form of "A------ +2 B------ -10" on the display 76. When theoperator sees this command on the display 76, he rotates the dial 53c ofone adjustment screw mechanism 53 of the tilt correcting unit 51 whichis located at the fulcrum A forward by two graduations and the dial 53cof the other adjustment screw mechanism 53 thereof which is located atthe fulcrum B backward by ten graduations. The tilting of the probe tipprofile of each probe group is thus corrected so that all of probes 23can be more reliably contacted with the pads.

When the probe card 22 is newly set in the insert ring 18 through thecard holder 25 or exchanged with a new one, the displacement sensor 55which has been housed and stored in the autoloader 31 is carried out atfirst by the loader stage 34. It is pre-aligned, mounted on thewafer-mounted table 15 and then further aligned, while viewing itsimage, by the alignment unit to more accurately position it on the table15. The top level of the wafer-mounted table 15 and the level of the topelectrodes 56b of the displacement sensor 55 on the table 15 aredetected by the detector circuit 36 provided with the electrostaticcapacitance sensor 36a. The thickness D₁ of the displacement sensor 55is derived from the difference between these values thus obtained, andthen stored in the memory of the CPU 71 of the control system 70.

The wafer-mounted table 15 is set at its lowermost center referenceposition by the X-Y drive system 44, lifted to a predetermined level athigh speed by the elevation drive system 45 and then further lifted atlow speed. When the wafer-mounted table 15 is lifted in this manner, topelectrodes 56b at the detection areas a-d of the sensor body 56 on thetable 15 come to contact tips of the probes 23.

At this instant when the tips of the probes 23 are contacted with theelectrodes 56b, PVDF films 56a at the detection areas a-d of the sensorbody 56 generate voltages between the upper electrodes 56b and the lowerone 56c thanks to piezoelectric effect. These voltages thus generatedare detected by the voltmeters 61a-61d of the detector circuit 60 anddetection signals are applied to the CPU 71 of the control system 70.

Responsive to these detection signals applied from the detector circuit60, the CPU 71 confirms the tip levels of probe groups of the probe card22 and stores them in its memory. In short, the CPU 71 confirmsdistances Zh₁ of the wafer-mounted table 15 from its lowermost referenceposition and stores them in the memory, said distances ZH₁ beingconfirmed at those instants when the detection areas a-d of the sensor55 are contacted with tips of their corresponding probe groups.

The wafer-mounted table 15 is then lowered to its lowermost referenceposition. From results obtained by the CPU 71 while confirming the probetip profiles, the tilt correcting circuit 75 arithmetically calculatesthe tilting degrees and directions of probe tip profiles and shows acorrection command on the display 76.

When all of the detection areas a-d of the displacement sensor 55 arecontacted with probe tips of their corresponding probe groups at thesame time, detection signals are applied to the CPU 71 at the same time,too. "A------ ±0 B------ ±0" is therefore displayed on the display 76and no tilt correction is needed in this case.

When the detection areas a-d of the displacement sensor 55 are contactedwith probe tips of their corresponding probe groups at differenttimings, those instances when detection signals are applied to the CPU71 become different. In short, some detection signals are applied fasterto the CPU 71 but others are slower. The CPU 71 arithmeticallycalculates the tilting degrees and directions of tip levels of probegroups in this case and causes the display 76 to display table supportlevels at fulcrums A and B like "A------ +2 B------ -10", for example.When seeing this, the operator rotates dials 53c at the fulcrums A andB, respectively. The tilting of probe tip profile of probe groups isthus corrected to thereby enable all of the probes 23 to be reliablycontacted with the pads.

When the tilting of probe tip profile is corrected in this manner, thedisplacement sensor 55 of the contact type is picked up from thewafer-mounted table 15, which has been lowered to its lowermostreference position, by the wafer handling arm 35 and returned to itsoriginal position in the autoloader 31 by the loader stage 34. A firstwafer 14 which is to be practically tested as carried out of the wafercassette in the autoloader 31, pre-aligned and then mounted on thewafer-mounted table 15 by the wafer handling arm 35. It is furtheraligned through an image confirming system in the alignment unit andthus accurately positioned and held on the table 15, which is thenreturned to its lowermost reference position. Before and after thisprocess, top levels of the wafer-mounted table 15 and the wafer 14 onthe table 15 are detected in the alignment unit.

The CPU 71 calculates a thickness D₂ of the wafer 14 from the differenceof values thus obtained, and then a difference ±Δ (D₁ -D₂) betweenthicknesses D₁ and D₂ of the displacement sensor 55 and the wafer 14.Further, this difference ±Δ is added to the level ZH₁ of thewafer-mounted table 15 previously obtained at the time when the top ofthe contact type displacement sensor 55 were contacted with tips ofprobes 23 to thereby calculate a contact level ZH₂ (=ZH₁ +(±Δ)) at whichthe wafer 14 lifted is practically contacted with tips of probes 23.This contact level ZH₂ denotes the contact point of the wafer 14relative to probes of the probe card 22 practically set. The distanceover which the wafer-mounted table 15 is lifted from its lowermostreference position is set equal to the contact point ZH₂. In thepractical case, however, the wafer-mounted table 15 lifted is set in theZ direction movement control circuit 73 as the over-driven distanceadded to about 50-100 μm from contact point.

When the wafer-mounted table 15 is lifted in this manner, electrode padson semiconductor chips of the wafer 14 can be more reliably contactedwith probe tips of their corresponding chip groups and electric propertyof each semiconductor chip can be thus more accurately checked, whilepreventing the wafer from being incorrectly contacted with probe tips orstruck against them to become broken. When test to the first wafer 14 asfinished, the wafer 14 is returned into the wafer cassette 32 in theautoloader 31 and same process will be applied to each of wafers 14followed.

When the thickness of the contact type displacement sensor 55 is madesame as that of the wafer 14, the contact point can be obtained withoutconducting any thickness detection through the electrostatic capacitancesensor 36.

Although the contact type displacement sensor 55 has four detectionareas a-d in the above-described case, it may have three or more thanfive detection areas.

Although the contact type displacement sensor 55 is made in the abovecase as an attachment detachably mounted on the wafer-mounted table 15only when needed, it may be made as a member held on the table 15 at alltimes.

Although the tilting of the insert ring 18 is directly corrected (whilethat of the probe card 22 as indirectly corrected) in the above case,the head plate 17, instead, may be directly corrected. When it is madeso, the space which is occupied by the ball hinge and support leveladjustment screw mechanisms 52 and 53 can be made fully larger anddesign freedom for these mechanisms can be made by far wider.

Each support level adjustment screw mechanism 53 may use a ball screwhaving an autodrive motor instead of the manual adjustment screw systemprovided with the graduated dial. The autodrive motor is electricallyconnected to the tilt correction circuit 75 of the control system 70 inthis case. Responsive to correction command signal applied from the tiltcorrection circuit 75, therefore, the motor is rotated forward andbackward to change the support level of the insert ring 18 or head plate17 through the ball screw. The tilting of probe tips can be thusautomatically corrected.

A contact-check-programmed tester capable of confirming whether or notprobes are contacted with a conductive dummy plate may be used as probetip profile detector dummy. Probe tip profile of plural probe groups aredetected in this case responsive to signal applied from the tester andalso on the basis of the distance over which the table 15 is lifted fromits lowermost reference position.

A CCD camera through which irregular probe tip levels of plural probegroups of the probe card 22 practically set are confirmed, and adetector circuit for detecting probe tip profile of them from the focusdepth of this camera may be used as probe tip profile detector means.

As shown in FIG. 8, a wedge member 79 arranged between the head plate 17and the insert ring 18 may be pushed or retracted to correct the tiltingof the probe card 22 as well as that of the insert ring 18.

A second embodiment of the present invention will be described withreference to FIGS. 9 and 10. Same components as those of the firstembodiment will be described only when needed.

In the second probe apparatus, the probe card 22 is positioned andsupported under the test head 27, which is arranged rotatable anderectable on the top on the apparatus body 11, through a card holder 81.

In the second probe apparatus, the card holder 81 is supported on thecenter underside of the test head 27 at three points thereof by a tiltcorrection unit 91. When the tilt correction unit 91 is adjustedresponsive to support level correction commands, the tilting of theprobe tip profile of each probe group of the probe card 22 can becorrected. The card holder 81 includes a cylindrical holder body 82which also serves as the contact ring, and a ring-shaped holder member83 for holding the probe card 22 under the holder body 82 by positioningpins and fasteners. Three protrusions 84a, 84b and 84c are projectedradially and outwards from the top rim of the holder body 82.

The tilt correction unit 91 hangs the card holder 81 from the bottom ofthe test head 27 through three protrusions 84a-84c. A ball hingemechanism 92 is arranged at one of three hanging points and supportlevel adjustment screw mechanisms 93 at other two handing points. Theball hinge mechanism 92 is substantially same as the one used in thefirst probe apparatus.

Each support level adjustment screw mechanism 93 is of the motorautodrive type. It includes a motor 93a, a ball screw 93b and a screwfeeding nut 93c. The motor 93a is fixed to a frame 27b in the test head27. The ball screw 93b is passed through the protrusion 84b to serve asa vertical rod or axis and it is rotated forward and backward by themotor 93a. The screw feeding nut 93c is fixed to the underside of theprotrusion 84b and screwed onto the ball screw 93b.

A CCD camera 100 and a detector circuit 102 are provided as means fordetecting the probe tip profile of each probe group. The CCD camera 100is attached to the side of the wafer-mounted table 15 in the apparatusbody 11 to check probe tip profiles of plural probe groups of the probecard 22. The detector circuit 102 is intended to detect probe tipprofile of plural probe groups on the basis of focus depths of CCDcamera 100.

The probe tip profile detecting operation conducted by the second probeapparatus will be described.

The CCD camera 100 is moved right under the probe card 22, whilecontrolling the movement of the wafer-mounted table 15, and probe tipsof some of probe groups are enlarged and checked through the camera 100.Probe tip profiles of these probe groups are detected on the basis ofthose focus depths of the camera, which are obtained when the probe tipsof them are checked through the camera, by the detector circuit.Detection signals thus obtained are applied to the tilt correctioncircuit 75 to arithmetically calculate the tilting degrees anddirections of probe tip profiles of them. The results are displayed on adisplay 101.

Responsive to correction command signals, the motor 93a of each supportlevel adjustment screw mechanism 93 of the tilt correction unit 91 isdriven to rotate the ball screw 93b forward and backward. When the levelof the card holder 81 is changed at two points of the holder 81 in thismanner, the card holder 81 is tilted, taking the ball hinge mechanism 92as a fulcrum, to thereby automatically correct the tilting of the probetip profile of each probe group.

A third embodiment of the present invention will be described, referringto FIGS. 11 through 13. Same component as those of the first and secondembodiments wall be described only when needed.

As shown in FIGS. 11 and 12, support frames 16 are erected on thesupport 12 of the probe apparatus body 11 and support sections 111 and112 are provided in the support frames 16 to support the test head 27.One of them is a fixed one 111 and the other remaining three are movableones 112. Each movable section 112 includes a test head adjustmentmechanism 113 for moving up and down, taking the fixed support section111 as a reference point, to adjust the tilting of the test head 27.

A motor 115 of the mechanism 113 is arranged in a hollow 114 of thesupport frame 16. The drive shaft of the motor 115 is connected to ascrew rod 116, which is screwed into a slider 117.

The shape of the slider 117 is rectangular in section, the slider 117 isnot rotatable relative to the support frame 16 but slidable in it in itslongitudinal direction. When screw rod 116 is rotated, the slider 117 ismoved up and down.

As shown in FIG. 12, a ball-like support 117a is formed on the top ofthe slider 117 and it is same in shape as the one at the fixed supportsection 111.

A support seat 118 is attached to the underside of the test head 27. Arecess 118b is formed in the underside of the support seat 118 and itreceives the ball-like support 117a. In short, the test head 27 issupported at four corners or points thereof by the ball-like supports117a.

Each of the support sections 111 and 112 is provided with a clampmechanism 119 for connecting the test head 27 to the support frame 16.Each clamp mechanism 119 includes a base 120 fixed to the support 117a,a rod 121 erected on the base 120, a pivot pin 122 arranged in the upperend of the rod 121, and a swing lever 123 swingable round the pivot pin122. The swing lever 123 has at the front end thereof a contact 124contactable with a shoulder 118a of the support seat 118 fixed to thetest head 27 and it is connected to an air cylinder 125 at the base endthereof. When the base end of the swing lever 123 is pushed up by theair cylinder 125, the contact 124 thereof is contacted with the shoulder118a of the support seat 118 to push the test head 27 against thesupport frame 16 through the support seat 118. The test head 27 can bethus fixed to the support frame 16.

The main stage 13 having the wafer-mounted table 15 is supported,movable horizontally along a stage guide 126, by the base 12. The stageguide 126 serves as a horizontal reference plane for the wafer-mountedtable 15.

A camera fixing arm 127 is horizontally and outwards projected from thewafer-mounted table 15 and an optical system or a television camera 128is mounted, as means for checking the parallel of probes, on the camerafixing arm 127. The television camera 128 is moved together with thewafer-mounted table 15, while opposing to the probe card 22. It isintended to optically measure the tilting of the probe card 22 or probes23 relative to the stage guide 126 which serves as the horizontalreference plane.

The television camera 128 is electrically connected to a control circuit129, which serves as control means, and detection signal relating to theparallel of probes 23 to the horizontal reference plane or stage guide126 is applied to the test head adjustment mechanism 113 through thecontrol circuit 129. The adjustment mechanism 113 can be thuscontrolled.

The operation of the third probe apparatus will be described below.

The test head 27 is supported by the fixed and movable support sections111 and 112. The base end of each swing lever 123 is pushed up by theair cylinder 125 of each clamp mechanism 119. The contact 124 of theswing lever 123 is thus contacted with the shoulder 118a of the supportseat 118 to force the test head 27 against each support frame 16 throughthe support seat 118. The test head 27 can be thus fixed to the supportframes 16.

The tilting of the probe tap profile of each probe group is optacallymeasured by the television camera 128 while moving the wafer-mountedtable 15 in directions X and Y.

When probes 23 of the probe card 22 are tilted relative to a referenceline P as shown in FIG. 13 the control circuit 129 measures the level atthe lowermost point J and that at the highest point K to obtain adifference Z₁ between them. At the same time, distance L₁ from the pointa to the point K is also calculated. Distance L₂ between two test headadjustment mechanisms 113 which support the test head 27 is certain.From distances L₁, L₂ and difference Z, therefore, tilting distance Z₂and angle θ₁ are calculated.

Responsive to control signal applied on the basis of results calculatedby the control circuit 129, each adjustment mechanism 113 is madeoperative. In short, motors 115 on the side of the point a are rotatedforward and those 115 on the side of the point K backward. Sliders 117on the side of the point J are thus lifted and those on the side of thepoint K lowered. The tilting of the test head 27 can be thus correctedto keep the probe tip level of each probe group parallel to the stageguide 126.

While using that portion of the test head, which is supported by thefixed support section 111, as the horizontal reference plane instead ofthe stage guide 126, only the adjustment mechanisms 113 of the movablesupport sections 112 may be moved up and down.

The test head 27 may be adjusted parallel while keeping the clampmechanisms 119 released and then clamped by them.

A fourth embodiment of the present invention will be described withreference to FIG. 14. Same components as those of the above-describedembodiments will be described only when needed.

A television camera 130 is attached to the heat plate 17 which serves asa horizontal reference plane for the probe apparatus body 11. It isopposed to the wafer-mounted table 15 to measure the parallel of thewafer 14 on the wafer-mounted table 15. When the wafer 14 is curved, ittilts relative to the top of the wafer-mounted table 15. This tilting ofit is measured and the tilting of probes 23 of the probe card 22 iscorrected through the test head 27 on the basis of results thusmeasured.

The television camera 130 is electrically connected to a control circuit129 which serves as control means. The control circuit 129 can controlthe adjustment mechanisms 113 in such a way that parallel detectionsignals of probes 23 and the wafer 14 relative to the state guide 126,which serves as the horizontal reference plane, are applied from thecontrol circuit 129 to the adjustment mechanisms 113.

The wafer-mounted table 15 is moved in directions X and Y, while holdingthe wafer 14 on it, and the parallel of the wafer 14 is measured atthree points thereof by the television camera 130. θ₂ x and θ₂ y (whichare the X-axis and Y-axis components of θ₂ of FIG. 14) are calculatedfrom values Z thus obtained and applied to the control circuit 129 asparallel detection signal of the wafer 14.

On the other hand, the probe tip level of each probe group is measuredthrough the television camera 130 and values thus obtained are applied,as parallel detection signal of the probes 23, to the control circuit129.

Responsive to tiltings θ₁ and θ₂ of probes 23 and wafer 14 applied, thecontrol circuit 129 calculates "θ₁ -θ₂ " and a result thus calculated isapplied, as control signal, to each adjustment mechanism 113 to make itoperative.

According to the above-described embodiment, the tilting of probes 23can be corrected while moving the test head 27 up and down on the basisof both data relating to tiltings of the wafer 14 and probes 23 of theprobe card 22. The electric property of each semiconductor chip can bethus more accurately checked.

According to the probe apparatus of the present invention, the probe tipprofile tilting of each probe group which is caused by making andattaching errors and deformation of the probe card can be detected andcorrected by far more easily and reliably while keeping the probe cardpractically set. The setting of the probe card assembly can be thus madeby far easier and the contact accuracy of probes relative to theelectrode pads can be enhanced to make test accuracy higher.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A probe apparatus for correcting the posture of aprobe card before a test to align probes with an object to be testedand, then, to bring the probes into contact with said object for testingan electric circuit of the object, comprising:a table on which an objectto be tested is mounted, said object having a circuit connected to aplurality of pads; a probe card assembly positioned relative to areference plane, and having a card body and groups of probes held on acard holder; lifter means for moving the objected-mounted table up anddown to cause the pads of the object to be contacted with probe tips ofprobe groups; a test head for applying a test signal to the circuit ofthe object through the probes and pads, which are contacted with oneanother, to test the electric property of the circuit; detector meansfor detecting probe tip profiles or levels at plural points of the probecard assembly; correction command means for calculating a tilting degreeand direction of each probe group from results thus detected to sendcorrection commands; a head plate fixed to an apparatus body frame; aninsert ring arranged between said head plate and said card holder; aball hinge mechanism pivotally supporting at one point at least one ofsaid card holder, said insert ring, and said head plate; and a pluralityof tilt correction mechanisms each supporting at one point at least oneof the card holder, the insert ring, and the head plate, the supportedmember being supported at a plurality of points by said tilt correctionmechanisms and the supported point being movable in a verticaldirection, such that the height of the supporting points of any of thecard holder, the insert ring, and the head plate is changed inaccordance with the command given from said correction command means soas to enable the level of the probe tips to be substantially parallelwith said reference plane.
 2. The probe apparatus according to claim 1,wherein said tilt correction mechanisms are a plurality of screwmechanisms each supporting at one point at least one of the card holder,the insert ring, and the head plate, the supported member beingsupported at a plurality of points by said tilt correction mechanismsand the supported point being movable in a vertical direction.
 3. Theprobe apparatus according to claim 2, wherein the stroke of at least oneof the card holder, insert ring and head plate moved by the leveladjustment screw mechanisms is 1000 μm, maximum.
 4. The probe apparatusaccording to claim 2, wherein each of said plurality of screw mechanismshas a manual adjustment screw provided with a graduated dial.
 5. Theprobe apparatus according to claim 1, wherein at least one of saidplurality of tilt correction mechanisms includes a ball screw providedwith an autodrive motor.
 6. The probe apparatus according to claim 1,wherein said insert ring is connected to and supported by said headplate through said ball hinge mechanism and said plurality of tiltcorrection mechanisms such that said insert ring is supported at atleast three points, and wherein the card holder is positioned relativeto the head plate through the insert ring.
 7. The probe apparatusaccording to claim 1, wherein said card holder is disposed below thetest head and is supported by the test head through said ball hingemechanism and said plurality of tilt correction mechanisms such thatsaid card holder is supported at at least three points.
 8. The probeapparatus according to claim 1, wherein the detector means comprises acontact type displacement sensor set on the object-mounted table andhaving plural individual detection areas which contact probes, and adetector circuit for detecting voltage changes caused when eachdetection area of the contact type displacement sensor is contacted by aprobe, and wherein levels of probe tips are detected at plural sectionsin response to at least one signal from the detector circuit and on thebasis of a distance over which the table is lifted.
 9. The probeapparatus according to claim 1, wherein the probe tip profile detectormeans includes a camera for taking an image of probe tips at pluralsections and a detector circuit for detecting levels of probe tips fromfocus depths of the camera at plural sections.
 10. The probe apparatusaccording to claim 1, wherein the probe tip profile detector meanscomprises a conductive dummy plate set on the table and which contactsprobes, and a tester having a contact check program to check whether ornot probes are in contact with the dummy plate, and wherein the probetip profile is detected at plural sections in response to at least onesignal from the tester and on the basis of a distance over which thetable is lifted.
 11. A probe apparatus for correcting the posture of aprobe card before a test to align probes with an object to be testedand, then, to bring the probes into contact with said object for testingan electric circuit of the object, comprising:a table on which an objectto be tested is mounted, said object having a circuit connected to aplurality of pads; a probe card assembly positioned relative to areference plane, and having a card body and groups of probes held on acard holder; lifter means for moving the object-mounted table up anddown to cause the pads of the object to be contacted with probe tips ofprobe groups; a test head for applying a test signal to the circuit ofthe object through the probes and pads, which are contacted with oneanother, to test the electric property of the circuit; a ball hingemechanism pivotally supporting one point one of said test head; and atest head adjustment mechanism for movably supporting in a verticaldirection the test head at a plurality of points to adjust the tilt ofthe test head so as to make the test head parallel to said referenceplane; probe measuring means attached to the table to measure theparallel of probes to the reference plane; and control means forcontrolling said test head adjustment mechanism to adjust the tilt ofthe test head, responsive to detection signals applied from the probemeasuring means, so that a probe tip profile can be kept parallel to thereference plane.
 12. The probe apparatus according to claim 11, whereinthe test head adjustment mechanism includes a motor arranged in theapparatus body, a screw rod rotated by the motor, and a slider screwedonto the screw rod and moved up and down, as the screw rod is rotated,while supporting the test head.